Spreading of Polar and Atlantic Water Masses

into the inner Nordic Seas Analyses of hydrographic measurements from Argo floats and Seagilders

Katrin Latarius, Ursula Schauer and Torsten Kanzow

katrin.latarius@awi.de

Argo User Workshop 2015, March 16-17, Brest, France

Outline of the following..

I. Large scale: Interannual to longer-term variability of salinity/freshwater in the Greenland Sea Basin Data: measurements with Argo floats

II. Mesoscale: Intrusion of freshwater from the ice edge/East Greenland Current to the inner Greenland Sea Basin Data: high resolution Seaglider sections

The Nordic Seas – where Polar and Atlantic water masses meet

E.P. Oberlander, WHOI

The Nordic Seas – Schematic of the system

Latarius & Quadfasel, submitted to DSR 2015

The Nordic Seas – Focus on the Greenland Sea

Argo float measurements in the northwestern Nordic Seas

Greenland Sea Basin: 1396 profiles 2001 to 2015 on average: 9 profiles per month

Time series of hydrography – Greenland Sea Basin 2001 to 2015

Increasing temperature and salinity in the time span of observations. Interannual variability of convection depth. Increasing T and S in the Atlantic inflow to the Nordic Seas: Faroe-Scotland-Channel: T: + until 2003 (2005/06 still high) S: + 1996-2006 Propagation with the circulation around the Nordic Seas; 3 to 4 years later in Fram Strait (Holliday et al., 2008)

Focus on salinity time series from the Greenland Sea

From surface to great depths

freshwater in the surface layer

From surface to great depths

salinity changes in the Atlantic layer

spreading in the vertical forced by convection

From surface to great depths

salinity increase from below

freshwater in the surface layer:

freshwater in the surface layer:

Sigma 28.0 27.6

freshwater in the surface layer:

Sigma 28.0 27.6

?

freshwater in the surface layer: summary

Relation between surface salinity and convection depth but also heat loss to the atmosphere, wind field, stratification below the surface layer influence the convection depth Another open question: Where is the variability of freshwater in the surface layer coming from Sources of freshwater: Liquid outflow from the Arctic Ocean (via Fram Strait) Ice melt, locally and remote

salinity changes in the Atlantic layer

salinity changes in the Atlantic layer

Lateral input of Atlantic Water is concentrated in 50 to 600 m (Latarius, 2013)

salinity changes in the Atlantic layer

salinity increase from below

salinity increase from below

Summer CTD-data from the central Greenland Sea: 1981-2003 Karstensen et al., 2005 2004-2013 ICES, PANGAEA, IMR; Andreas Wisotzki

salinity increase from below

Somavilla et al., 2013 Isopycnal spreading of Arctic Ocean deep waters into the inner Greenland Sea Salinity 2000 m to bottom 1995 to 2010 S: +0.01

salinity increase from below

CTD

Argo

Salinity increase in the Atlantic layer and from below met in the last years

From Argo floats to gliders

from large scale to mesoscale..

Lherminier et al., 1999: Pot. T 420m, CTD

N. Serra, pers cummunication, 2010: Snapshot, MITgcm, 4 km hor resolution

vel 500m depth, pot Vorticity red-positiv, blue-negative

Glider measurements at the Polar Front – Western Greenland Sea

Spitz- bergen

Glider measurements at the Polar Front – Western Greenland Sea

Altogether: 60 days of mission with 2 gliders 700 dives (0-500m or 0-1000m) 4 E to W-sections 6 SE to NW sections

in the following: concentration on SE to NW salinity sections..

Ice

9 days

ICE ICE

9 days

558/120-192

7 days

6 days

558/192-244

13 days

8 days

558/244-306

8 days

16 days

127/101-168

6 days

Glider sections between Polar Front and central Greenland Sea

Smean (surface to sigma 27.5) = 33.0 ~ 7 days S: -0.18 Smean (surface to sigma 27.5) = 32.82 ~ 9 days S: +0.37 Smean (surface to sigma 27.5) = 33.19

Glider sections between Polar Front and central Greenland Sea

Smean (surface to sigma 27.5) = 33.00 ~ 0 days S: -0.05 Smean (surface to sigma 27.5) = 32.95 ~ 6 days S: -0.09 Smean (surface to sigma 27.5) = 32.86

Glider sections between Polar Front and central Greenland Sea

„freshwater features“ have horizontal scales of 10 to 40 km matches well with the baroclinic Rossby-Radius

Hovmüller diagram build from the glider sections

14 years of Argo float measurements in the Nordic Seas enable to observe long term and large scale development of the system. The combination with observations from below 2000m and with observations with higher resolution in space and time opens the perspective for interpretation.

..

end

I. freshwater in the surface layer: